The adenylyl cyclase inhibitory pathway is differentially modified
in rat white and brown fat by high-energy diets1.
Kenan, Yael, Martha Levinson, Mark Pines, and Michael Naim.
Institute of Biochemistry, Food Sciences and Nutrition, The Hebrew
University of Jerusalem, Rehovot 76100 and Institute of Animal
Science, Volcani Center, Bet Dagan 50250, Israel
APStracts 4:0021E, 1997.
Incubation of white adipose tissue (WAT) adipocytes from rats fed a
high-energy diet (EXP group) with the antilipolytic, Gi-coupled
adenylyl cyclase inhibitory agonists nicotinic acid (NIC) and N6 -(L
-2-phenylisopropyl)-adenosine (PIA) resulted in lower cellular cAMP
levels than in stimulated adipocytes from rats fed a nutritionally
balanced diet (CON group). In contrast to WAT, incubation of brown
adipose tissue (BAT) adipocytes with NIC yielded higher cAMP levels
in the EXP vs. CON rats. In both WAT and BAT adipocytes, pertussis
-toxin treatment abolished the differences in NIC- and PIA-inhibited
cAMP formation between EXP and CON animals. Immunoblotting of
adipocyte membranes indicated a lower content of Gi[alpha] but not
Gs[alpha] in BAT membranes of EXP vs. CON animals after 6 and 10
weeks of feeding. No such differences were found in the Gs[alpha] or
Gi[alpha] contents of WAT membranes. Thus, the inhibitory pathway of
adenylyl cyclase is proposed to be sensitized in WAT and desensitized
in BAT of rats fed high-energy diets. These modifications in
sensitivity are in line with reduced cAMP and lipolysis in WAT and
increased cAMP and thermogenesis in BAT during obesity.
Received 24 September 1996; accepted in final form 23 January
1997.
APS Manuscript Number E482-6.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 19 February 1997